Layout attached property not available to SplitView children

The Layout.* attached properties are not available to the SplitView children: running the attached test case leads to an error:

file:///tmp/main.qml:56 Non-existent attached object

The problem goes away if I uncomment the line importing QtQuick.Layouts.

Either the documentation for SplitView should be fixed to include the information about the need of importing QtQuick.Layouts, or the importing should not be required.